On Debian

You can install the perl modules using CPAN, or there are RPM and DEB packages as well. We generally recommend sticking to the distribution packages, to make updating your system easier. The Centos packages are mentioned on that page. If you are running a Debian based system just run:

apt-get install dkimproxy

It will install the necessary dependencies, generate your keys and even start up the proxy server for you. You will find your keys in /var/lib/dkimproxy/. You will need to follow Brandon's guide to setup your DNS records, and double check the configuration Debian installed is what you want. Check the hostname and selector name match your setup for instance here:

/etc/dkimproxy/dkimproxy_out.conf

I found that Debian uses "postfix" as the selector name, but we typically use "mail" or "selector1" so normally need to change this: